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JMB1943

Royal Artillery---Accuracy of 13/18 pdrs & 6/8" howitzers

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JMB1943

This is not a question about relative merits of British & German artillery fire.

 

I have a grandfather who served in 228th Siege Battery, RGA; this unit was variously equipped with 8" and 6" howitzers.

All things being equal, how far apart were the field-pieces of any given battery separated?

My initial assumption is that any particular gun would be distanced far enough from its neighbour to be outside the beaten zone of the German gun-battery.

My second assumption is that this German beaten zone is approx. the same as that of the RA.

 

Can anyone provide numbers for accuracy, e.g., figure of merit / beaten zone / zone with 50% of shells etc, for the field-pieces mentioned in the title?

 

Regards,

JMB

 

 

 

 

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JMB1943

I have eventually tracked down some real numbers related to the accuracy of British heavy ordnance, as shown in the Table.

These data are for an 8" B.L., Mk IV, elevation: 5 deg. 36 min; muzzle velocity: 2045 ft/sec.

*Text Book of Gunnery, Maj. G. Mackinlay, RA; London (1887), p.170                                                              

Number

Of round

Range

(yds)

Difference

From Mean

Deviation

Right (yds)

Difference

From Mean

 

 

1

4968

22.8

24.4

3.0

 

 

2

4954

8.8

21.6

0.2

 

 

3

4962

16.8

22.8

1.4

 

 

4

4908

37.2

20.0

1.4

 

 

5

4934

11.2

18.4

3.0

 

 

Sum

24726

96.8

107.2

9.0

 

 

Mean

4945.2

19.4

21.4

1.8

 

 

 

 

The mean longitudinal (range) error is 19.4 yds & the mean lateral (deviation) error is 1.8 yds.

It turns out that 50% of shots are expected to land within 1.69 x the given error.

This length zone is then 1.69 x 19.4 = 33 yds, so these shots are contained in a distance (33/2 yds) i.e. 16.5 yds ahead of and behind the target.

Similarly, the breadth zone is 1.69 x 1.8 = 3 yds.

The length zone and the breadth zone are at right angles to each other; if they are superimposed, a rectangle is formed which will contain 50% of 50% (i.e. 25%) impacts.

Apparently, at the time this was known as the 25% probable rectangle.

"The relative accuracy of different guns at different ranges is estimated by the dimensions of this rectangle."*

The practical effect of this is, that this 8" gun will strike a wall of 12 ft x 12 ft only 30 shots out of 100, at an accurately known range of 4945 yds.

 

Regards,

JMB

 

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